These methods and facilities are characterized in by the kind of transmission of the driving forces required for this process. The two main principles of transmission are the positive and the non-positive transmission. With the underfloor processing method, generally the non-positive drive is used. The efficiency of a wheelset processing facility with a non-positive drive of the wheel is mainly determined by how it is managed to transfer the driving forces onto the wheelsets. The simpliest way to increase the driving forces that may be transmitted is to increase the pressing force (normal force) of the friction rollers concerned. However, high normal forces result in an unadmissible excursion of the wheelset centre line away from the processing rotation axis.
Another way is to minimize the slip between friction roller and wheelset. In this direction, intensive work on the improvement of wheelset processing methods and wheelset processing facilities has been done for many years (DE-PS 14 77 587, DE-AS 20 63 074, DE-OS 29 37 751, DE-PS 30 12 997). With the DE-OS 39 31 747, the weight of the wheelset is optimized by allocation of friction roller and tool one to another and to the straining line. Apart from that, there are proposals aimed to increase the number of friction rollers. That results in a load distribution but does not help to abolish the a/m problems resulting from the non-positive drive.
In order to use the limited friction forces between the wheelset and the friction rollers, later the same inventor found with the EP 491 067 a method for limiting a slip (and, in addition, with the PS 40 01 793, a method for determing the slip) for this processing task. With this method, the slip between the friction roller and the driven wheelset is permanently measured; when the preset upper limit value of the slip is reached, the cutting cross section of the tool is reduced by appropriate control technological measures, and when the preset lower limit value of the slip is reached, the chip cross section is increased again. In this sense, this instruction is--particularly when the level of technology cited there is complied with--an optimizing instruction for processing at the critical border.
However, all these proposals have the disadvantage that the resulting tangential components of the tool forces onto the wheelset are not reduced and hence further must be transferred by the friction rollers with full power.
It is also the general level of technology that with underfloor wheelset processing machines with bearing box centering, load facilities for increasing the normal force are required during the processing operation. For this reason, with underfloor wheelset lathes outer and/or inner holding down appliances are provided to additionally reduce the small space available at the wheelset.
The use of several tools (lathe chisel or milling cutter) is generally known also for the field of application `wheelset processing`.
In DE-PS 14 77 587, two lathe chisels displaced by 180.degree. are used. That ensures that the tool force components produced by every individual tool onto the wheelset partially compensate one to another. The only disadvantage with this solution is that the components of the tangential forces of the tools add up.
With the DE-PS 5 66 201/H9870 lb/49b, a wheelset milling machine fitted with several milling cutters for processing wheelsets is provided. With this project, every milling cutter has different processing tasks (tread and flange as well as rim). The driving tongues at the faceplates of the spindle heads drive the wheelset mounted in the centres with a positive drive. The profile roller cutters for tread and flange processing have each the same direction of rotation, and the double-face cutters for rim side processing work in counterdirection. The different processing tasks, different processing depths and different processing speed result in differences between the tool force components. Also the separate processing of wheel profile and face side result in differences in the tool force components, which assessment and effect are not the object of the invention. Thanks to the fact, that this wheelset milling machine processes wheelsets in the removed condition, the problems of power transmission (as with the non-positive drive) did not occur.
The problems of slip reduction must be considered only with non-positive drives. But also other wheel processing methods that have become popular until now stop with the compensation of the deforming tool forces and did not see the possibility of compensating the components of the tangential forces of the individual tool forces acc. to direction and amount and the efficient utilization of the driving forces produced by non-positive friction rollers, which resulted from the use of rotating tools.
However, the separate existence of solutions with rotating tools on the one hand, and the existence of problems with the transmission of forces with non-positive drives on the other hand, failed to result in the conclusion that with the use of rotating tools running in counterdirection with a non-positive drive the existing load transmission problems with this kind of drive could be solved.
The aim of the invention is a wheelset processing method and a wheelset processing facility of the kind mentioned in the beginning, mainly for underfloor processing, that render the possibility to increase the efficiency of the cutting operation without essential increase of the driving forces of the friction rollers, that provide a reduction of the normal forces required to produce the friction forces and thus permit also the lack or at least the reduction of additional load facilities, and together with that, obtain a reduction of the deformation at the wheelset and an improvement of the machining accuracy.
It is the task of the invention to provide a wheel processing method and a wheel processing facility that approximately compensate the forces produced by the rotating tools onto the wheelset in tangential direction.